骤然
zhoù rán · HSK 7
suddenly
🐎 骤然 = 骤 (gallop, horse radical 马) + 然 (-ly); a horse bolting = suddenly
骤 carries the horse radical 马 and first meant a horse breaking into a fast gallop, so it came to mean abrupt or sudden. 然 is the common manner suffix turning it into an adverb, giving骤然 = abruptly, all at once.